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I'm having a hard time remembering trig, and I have spent some time trying to solve this.

How do I find the coordinate of a point on a circle for certain angle if we know radius of circle and a center of circle coordinate?

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For a given angle $\theta$ and a circle of radius $r$ and center $(h, k)$, recall that we can determine the Cartesian coordinates $(x, y)$ of the point on the circle determined by $\theta$ and $r$, where $$x = h + r \cos \theta,\;\;y = k + r\sin \theta$$

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  • $\begingroup$ I'm not sure I understand, but how is this dependent on the coordinate of the circle center? Won't it be same for circle with same radius on any point? $\endgroup$ – Dvole Aug 25 '13 at 16:35
  • $\begingroup$ If the circle's center is not the origin, then we add $h$ to $x = r\cos\theta$ and $k$ to $y = r\sin\theta$. $\endgroup$ – amWhy Aug 25 '13 at 16:38
  • $\begingroup$ centres may not be same. $\endgroup$ – Suraj M S Aug 25 '13 at 16:40
  • $\begingroup$ how would the formula look like for a 3D circle? $\endgroup$ – Nicky Sep 6 '16 at 9:10
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if the centre of the answer circle is $(h,k)$,angle $\theta$,and radius $r$,then position of point is $$(h + r\cos\theta, k + r\sin\theta)$$

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